1. Field of the Invention
The present invention relates to an irrigation sleeve for an ultrasonic medical handpiece.
2. Background Information
There has been developed a medical procedure commonly referred to as phacoemulsification ("phaco") that is performed to remove a cataracteous lens. A phaco procedure includes the steps of making an incision in the cornea and inserting a tip that is manipulated by a surgeon to break and remove the lens. The tip is typically driven by an ultrasonic device which imparts a vibratory energy to the lens. The tip extends from a handpiece that is coupled to an irrigation line and an aspiration system. The irrigation line provides an irrigation fluid to the anterior chamber of the cornea. The aspiration system pulls the irrigation fluid and emulsified lens from the cornea.
FIG. 1 shows a typical surgical instrument 1 used to perform phaco procedures. The surgical instrument 1 includes an outer irrigation sleeve 2 that is attached to an outer case 3 of the instrument 1. An ultrasonically driven tip 4 extends from the case 3 and through the sleeve 2. The vibrating tip 4 is used to emulsify the lens of a cornea 5.
The case 3 has an irrigation inlet port 6 that is connected to an irrigation line. The irrigation line provides an irrigation fluid to the instrument. The sleeve 2 has an irrigation port (not shown) that allows the irrigation fluid to flow into the eye. The sleeve 2 is separated from the tip 4 to create a channel 7 that allows irrigation fluid to flow from the inlet port 6 to the outlet port. The tip 4 has an aspiration channel that is connected to an aspiration system. The irrigation fluid and emulsified lens are drawn through the channel 8.
The irrigation fluid must be provided at a sufficient pressure and flowrate to maintain the interocular pressure of the cornea without damaging corneal tissue. It is desirable to provide an incision opening that is large enough to allow the tip 4 and sleeve 2 to be inserted into the cornea without allowing the irrigation fluid to leak back out of the anterior chamber. This requires making an incision that is approximately the same size as the outer diameter of the sleeve 2.
The cornea tissue about the incision may create frictional contact between the inner surface of the sleeve and the oscillating tip. The frictional contact between the sleeve and the tip creates heat. The heat may burn the endothelium tissue of the cornea. Damage to the endothelium is irreversible and may result in a permanent impairment of the patient's vision. It is therefore important to avoid corneal burning during a phaco procedure.
U.S. Pat. No. 5,354,265 issued to Mackool discloses an ultrasonic handpiece which has a flexible outer sleeve and a hard inner sleeve. The hard inner sleeve may reduce the amount of contact between the outer sleeve and the vibrating tip. The reduction in contact decreases the heat and probability of corneal burning. U.S. Pat. No. 5,282,786 issued to Ureche and U.S. Pat. No. 5,807,310 issued to Hood disclose irrigation sleeves that have bands which are constructed from a material such as TEFLON. The TEFLON sleeves have a stiffness that is greater than the stiffness of the rubber material. The TEFLON outer band may reduce the friction and corresponding heat generated between the cornea and the irrigation sleeve.
As shown in FIG. 2, the cornea may apply nonsymmetric forces F.sub.1 and F.sub.2 (F.sub.1 &gt;F.sub.2) to the outer surface of the sleeve. The non-symmetric forces may push the inner sleeve into contact with the tip even with an inner sleeve or inner/outer bands disclosed in the prior art. The sleeve may make contact with the vibrating tip along the entire length of the tip to create a relatively large frictional area. Thus even with an inner sleeve or an inner/outer band the vibrating tip may still generate heat with the irrigation sleeve. It would be desirable to provide an irrigation sleeve that will reduce the likelihood of frictional contact between the sleeve and the vibrating tip.